cal legend, which says
that when the earth was being created God was flying over the peninsula
with a bag of huge boulders. The rocks were too heavy for the bag, and
it broke over southwestern Bulgaria.

Some Bulgarian geographers refer to the western Rodopi and the Pirin as
the Thracian-Macedonian massif. In this context, the Rodopi includes
only the mountains south of the Maritsa River basin. There is some basis
for such a division. The Rila is largely volcanic in origin. The Pirin
was formed at a different time by fracturing of the earth's crust. The
uplands east of the Maritsa River are not of the same stature as the
major ranges.

Sizable areas in the western and central Stara Planina and smaller areas
in the Pirin and in Dobrudzha have extensive layers of limestone. There
are some 2,000 caves in these deposits. The public has become more
interested in the caves during the past three or four decades, but only
about 400 of them have been completely explored and charted.

To the east of the higher Rodopi and east of the Maritsa River are the
Sakar and Strandzha mountains. They extend the length of the Rodopi
along the Turkish border to the Black Sea but are themselves
comparatively insignificant. At one point they have a spot elevation of
about 2,800 feet, but they rarely exceed 1,500 feet elsewhere.

Formation of the Balkan landmasses involved a number of earth crust
foldings and volcanic actions that either dammed rivers or forced them
into new courses. The flat basins that occur throughout the country
were created when river waters receded from the temporary lakes that
existed while the rivers were cutting their new channels. The largest of
these is the Sofia Basin, which includes the city and the area about
fifteen miles wide and sixty miles long to its northwest and southeast.
Other valleys between the Stara Planina and the Sredna Gora ranges
contain a series of smaller basins, and similar ones occur at intervals
in the valleys of a number of the larger rivers.

Drainage

From a drainage standpoint, the country is divided into two nearly equal
parts. The slightly larger one drains to the Black Sea, the other to the
Aegean. The northern watershed of the Stara Planina, all of the Danubian
plateau, and the thirty to fifty miles inland from the coastline drain
to the Black Sea. The Thracian Plain and most of the higher lands of the
south and southwest drain to the Aegean Sea. Although only the Danube is
nav